1. Field of the Invention
This invention relates to the field of stabilization of inorganic substrates, the prevention of leaching therefrom, and particularly to the stabilization of metals, metal ions and other inorganic ions in soils which have been contaminated.
2. Description of the Prior Art
Disposal of waste materials or materials inadvertently contaminated with metals, metal ions and other inorganic ions is extremely difficult and costly. There has been a long felt need for a safe and reliable process to stabilize inorganic substrates, especially soils to prevent leaching therefrom and to convert the inorganic substrate to a useful or at least, an innocuous material.
Sanforth in U.S. Pat. No. 4,889,640 describes a method for substantially reducing the leachability of lead and cadmium in foundry waste by treatment of the waste with calcium or magnesium carbonate.
U.S. Pat. No. 4,990,404 discloses that a carbon-sulfur polymer produced by the reaction of sulfur vapor with an organic material will bind any metals contained in the organic rendering them insoluble.
Weinwurm, et al. in European Patent Application EP 313,016 (Chem. Abstr. 111, 80889, 1989) describe a method for insolubilizing heavy metals in waste sludge by mixing with a plastic material, e.g. a clay or shale, capable of immobilizing leachable metals, and heat treating to form a stable silicate complex. This procedure involved pyrolysis and calcination in excess of 1000.degree. C.
Ader et al. in U.S. Pat. No. 4,884,815 teach that certain mercury-containing sludges can be rendered non-leachable or stabilized by treatment with sulfur and cement kiln dust. The sludge is preferably treated with caustic prior to adding the cement kiln dust. The waste sludges contain 20-35% water, and the patent teaches that sulfur reacts with the caustic to produce Sx.sup.-2 which, in turn, reacts with mercury salts to form mercury sulfide. There is no suggestion that sulfur alone would render metals and metal ions in soils or sands non-leachable.
Schwab, et al. in U.S. Pat. No. 2,203,881 teach an apparatus for injecting molten sulfur into voids in soil thereby stabilizing the soil. This reference does not suggest that the sulfur mixes with the soil or that leaching of metals or metal ions from soils treated by this process would be prevented.